Metal-ring stretching frequency

The local symmetry of the ring is reduced to in centrally bonded complexes with a resultant increase in the number of IR bands from four to seven (Table 4-9). In addition, a metal-ring stretching frequency is present in the far IR in complexes exhibiting this bonding mode. Some typical complexes in this class are listed in Table 4-10. 

The frequencies of columns 1 to 7 correspond to the seven n.v. of MCCjjHs) infrared-active in Cg, (cf. Table X). Column 8 lists the observed metal-ring stretching frequencies. The assignments of 1 and 2 are tentative, 1 being possibly the -representation vibration, the Ai vibration being unobserved. 

The series of dibenzene-metal complexes can be treated similarly. Table XLIV lists the asymmetric metal-ring stretching frequencies and the /... 

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